fixes

avr_code/defines.h

@@ -28,10 +28,12 @@ extern "C" {
 #define DO_UART true
 #define ITERATING false
 
-// Serial log line, compiled out entirely when DO_UART is off. The caller's
-// file must include uart.h (directly or via another driver header).
+// Serial log line, compiled out entirely when DO_UART is off. Takes a string
+// LITERAL only: PSTR keeps the text in flash instead of copying it into RAM at
+// boot. The caller's file must include uart.h (directly or via another driver
+// header). Use uart_sendString() for runtime strings.
 #if DO_UART
-#define LOG(msg) uart_sendString(msg)
+#define LOG(msg) uart_sendString_P(PSTR(msg))
 #else
 #define LOG(msg) ((void)0)
 #endif